In an example printing apparatus, printing materials, such as ink, resin, plastics or powders may be subjected to heat. For example, in an inkjet printer, ink fluid is deposited on a substrate. Heat may be applied to the printed substrate to evaporate a liquid component of the ink, such as water and/or solvent, to dry the printed substrate. In some examples the printed substrate is subjected to hot air or radiation emitted from an illumination source. The same may apply to the drying of three-dimensional (3-d) printed objects.